This invention concerns the treatment of certain alkyl diethanolamines to inhibit color formation therein during manufacture or to remove color-forming contaminants therefrom after manufacture. More particularly, it concerns the purification and reduction in color of an off-color N-(C.sub.4 -C.sub.10) di(C.sub.2 -C.sub.3) alkanolamine by the addition of a color inhibiting amount of a water-soluble metal borohydride to said alkanolamine, and subjecting the product in the presence of water to vacuum distillation at a pressure of less than about 50 mm.Hg (millimeters of mercury).
There exist a significant demand for high purity/low color N-butyl diethanolamine in the photographic market. However, the product, as manufactured, contains impurities and is off-color. Vacuum distillation at about 100 mm.Hg will remove much of the impurities but high color rapidly returns on storage indicating the continued presence of color forming compounds.